Solubility parameters for determining optimal solvents for separating PVC from PVC-coated PET fibers

Poly(vinyl chloride) (PVC) in PVC-coated poly(ethylene terephthalate) (PET) fabrics can be separated through dissolution in a suitable solvent, leaving only the PET fibers. We investigated the solubility of PVC in 30 solvents using swelling tests. The results were compared with those obtained using the Hansen, Gutmann, Swain, ET(30), and Kamlet-Taft parameters. For this purpose, Gaussian plots of the PVC swellability versus solubility parameter were used to decide the applicability of the solubility parameter system. Only Gutmann's electron acceptor-donor parameter (AN + DN) and the Kamlet-Taft parameters beta and pi* could describe the PVC-solvent system satisfactorily. Tetrahydrofuran (THF), methyl ethyl ketone (MEK), N, N-dimethylformamide (DMF), cyclohexanone, and cyclopentanone were tested for separating PVC from PET at different temperatures. THF dissolved PVC at 20 degrees C, while cyclohexanone and cyclopentanone did so at 40 degrees C. Traces of PVC remained on the PET fibers when DMF was used. Complete dissolution of PVC was not achieved at any temperature with MEK. The present work shows that solubility parameters are a helpful tool for the search for suitable solvents. It shows also that solubility parameters have to be selected carefully, since their usefulness depends strongly on the polymer properties.